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Generally, each molecule of plasmid diffuses randomly, so the probability of having a plasmid-less daughter cell is 2 1−N, where N is the number of copies. For instance, if there are 2 copies of a plasmid in a cell, there is 50% chance of having one plasmid-less daughter cell. However, high-copy number plasmids have a cost for the hosting cell.
The origin and function of meiosis are currently not well understood scientifically, and would provide fundamental insight into the evolution of sexual reproduction in eukaryotes. There is no current consensus among biologists on the questions of how sex in eukaryotes arose in evolution , what basic function sexual reproduction serves, and why ...
This is an accepted version of this page This is the latest accepted revision, reviewed on 11 February 2025. Cell division producing haploid gametes For the figure of speech, see Meiosis (figure of speech). For the process whereby cell nuclei divide to produce two copies of themselves, see Mitosis. For excessive constriction of the pupils, see Miosis. For the parasitic infestation, see Myiasis ...
Many protists reproduce sexually, as do many multicellular plants, animals, and fungi. In the eukaryotic fossil record, sexual reproduction first appeared about 2.0 billion years ago in the Proterozoic Eon, [64] [65] although a later date, 1.2 billion years ago, has also been presented.
[3] [10] The F-plasmid belongs to a class of conjugative plasmids that control sexual functions of bacteria with a fertility inhibition (Fin) system. In this system, a trans-acting factor, FinO, and antisense RNAs, FinP, combine to repress the expression of the activator gene TraJ. TraJ is a transcription factor that upregulates the tra operon.
The term plasmid was coined in 1952 by the American molecular biologist Joshua Lederberg to refer to "any extrachromosomal hereditary determinant." [14] [15] The term's early usage included any bacterial genetic material that exists extrachromosomally for at least part of its replication cycle, but because that description includes bacterial viruses, the notion of plasmid was refined over time ...
Among the many-celled groups are animals and plants. The number of cells in these groups vary with species; it has been estimated that the human body contains around 37 trillion (3.72×10 13) cells, [7] and more recent studies put this number at around 30 trillion (~36 trillion cells in the male, ~28 trillion in the female). [8]
Many biotechnology applications utilize mutated plasmids that replicate to high copy number. For example, pBR322 is a medium copy number plasmid (~20 copies/cell) from which several high copy number cloning vectors (>100 copies/cell) have been derived by mutagenesis, such as the well known pUC series. [1]